Ball forming mill



Oct. :22, Q D. E. WEL 2,409,6 9

BALL FORMING MILL Filed June 6, 1944 5 Sheets-Sheet 2 Y. & i

LQ i j i WWI m w 2 i U INVEN'IIOR. E SD. B. 3g- DAVID E.WEL S BY :3 o o ATTORNEYE Q Oct. 22, 1946. D. E. WELLS 2,469,649

BALL FORMING MILL Filed June 6, 1944 f s Sheets-Sheet s INVENTOR.

DAVID E. WELLS.

l N, m,mma

A YTORNE Y3 Oct 22, 1946: D. E. WELLS BALL FORMING MILL Filed June 6, 1944 5 sheeis sheet 4 ATTORNE Y5.

7 Oct. 22, 1946. D. E. WELLS BALL FORMING MILL Filed June a, 1944 5 Sheets-Sheet 5 LL ,P" l; pf; 7 AIRY I I I law H770? zyzs' Patented Oct. 22, 1946 UNITED STATES PATENT OFFICE BALL FORMING MILL David E. Wells, San Leandro, Calif.

Application June 6, 1944, Serial No; 538,985

The present invention rela es to improvements in a ball forming mill, and it consists of the combinations, constructions and arrangements hereinafter described and claimed.

An object of my invention is toprovidea ball forming mill, that is adapted for transforming heated rods into metal balls, the latter being completely shaped when delivered from the mill. It is further proposed to provide a mill in which the process of forming the metal balls may be carried out in a continuous manner and preferably at a relative high speed, whereby the production of the metal balls may be speeded up as compared with the method which is now employed for forming the balls. This application is a continuation-in-part of my co-pending application on a Ball forming mill, Serial No. 360,347, filed October 9, 1940.

A still further object is to provide a novel rodfeeding apparatus, which is adjustable for advancing the heated rods atthe desired speed into the ball forming section of the mill and for resiz ing the rod if necessary so that the correct amount of material will be fed into the ball forming section. This rod-feeding apparatus rotates the rods as they are advanced, and I provide a pair of coasting rollers or dies that are arranged for cutting the advancing rod into equal segments and then for. forming the latter into spherical metal balls. Therod-feeding apparatusrotates the rod at the same peripheral speed as the peripheral speed of the dies prior tothe rod entering the dies.

Another object of my invention residesin the provision of a pair of rod-cutting and ball-forming rollers or dies, the peripheries of which nearly contact with each other and whose axes practically parallel the axis or the advancing rod. These die rollers are fashionedwith spiral grooves therein, which cut the desired amount of material from therod and simultaneously form the cylindricalmaterial into a spherical ball while it is being cut.

It is further proposed to provide a rod-feeding apparatus that will cause the rod not only to rotate at the same peripheral speed as that of the rollers, but will advance the rod longitudinally at a speed which will obviate slippage between the rod and the roller helices. It is essential that the helices of the forming rollers be perfectly aligned with respect to one another, and I-provide novel means for accomplishing this result.

It is also proposed to provide a mill of the character described, which is adjustable for forming metal balls of various sizes.

Other objects and advantages will appear as the specification proceeds, and the novel features of my invention will beparticulariy set forth, in the claims hereunto annexed. i

For a better understanding of the; invention,

4 Claims. (01. 80-23) 2 1 reference should be had to the accompanying drawings, forming part of this application, in which:

Figure 1 is a longitudinal sectional View through the ball forming portion of the mill, commencing with the feeding and rod reducing end and extending as far into the driving unit as indicated by the broken lines a-b; 1 Figure 2 is a longitudinal section through the remaining part of the mill, starting with the same broken lines ab and continuing through the driving'unit, parts being shown in elevation;

Figure 3 is a transversevertical section taken along the line III-III of Figure 1;

Figure 4 is a front elevation of the millas see irom'the left-hand end of Figure 1;

Figure 5 is a vertical transverse section taken along the line V-V of Figure l;

Figure 6 is a plan View of the feed tube cooling box and top carrier, both of which will be better understood as the specification continues;

Figure '7 is a section taken along the line VIIVII of Figure 6;

Figure 8 is a plan view of the feed tube support,

taken along the line VIII- VIII of Figure 1;

Figure 9 is a vertical section taken along the line IX-IX of Figure 1; 1 v Figure 10 is a perspecive view of the ball guide and rest bar; s

Figure 11 is a partial sectional view taken along the line XI)H of Figure-1;

Figure 12 is a diagrammatic View of a circum ferential travel cutting cycle;

Figure 13 illustrates graphically the relative sizes of the cylindrical rod segment and th spherical ball formed therefrom; and 1 Figure 1a illustrates diagrammatically the steps of resizing the rod and forming the ball from a rod segment. 1

While I have shown only the preierred form of my invention, it should be understood that various changes or modifications may be made within the scope of the appended claims without sparting from the spirit or the invention.

The entire mill is illustrated in Figures 1 and 2. The rod resizing, feeding, cutting and ball forming portions of the mill are shown in Figure 1, while the drive and adjusting mechanism is disclosed in Figure 2'. The broken line web of Figure 1, if superimposed on the broken lined-b of Figure 2, will bring the two portions of the mill together and give a complete showing of the entire mill from end to end.

In describing the construction and operation of the mill, the rod resizing and feeding end will be mentioned first; then the rod cutting and ball forming portion of the mill; and, finally, the operating mechanism which actuates the entire mill. 7

Rod resizing and feeding assembly Referring now to Figures 1 and 4, it will be noted that I make use of a base A for supporting the rod resizing and feeding assembly, and this base is secured to a bed plate B by bolts I. Two guide posts 2-2 extend upwardly from the base A and slidably carry lower and upper rod resizing and feed roller carriers 3 and 3', respectively. The lower portions of the guide posts 22 are threaded and receive adjustable nuts 4 that bear against the lower carrier 3 and prevent vertical movement below a predetermined point. In a like manner, the upp r portions of th guide posts 2-2 are threaded and receive adjustable nuts 4 that prevent upward movement of the upper carrier 3' above a predetermined point. The purpose of these positive limits which will prevent movement of the carriers away from each other will be explained later.

The upper carrier 3' is similar in construction to the lower carrier and, therefore, a description of the lower one will suffice for both. Like reference numerals will be applied to corresponding parts of the two carriers, except the numerals will be primed for the parts associated with the upper carrier 3'. The carrier 3 has a central depression 5, which iscircular, with an axially disposed recess 6 (see Figure 1).

A rod resizing feed roller housing, indicated generally at C, has a disc-shaped platform 1 that is rotatably received in the depression 5 and a concentric circular extension 8 rotatably receivable in the recess 6. A bolt 9 secures the platform 1 in place, while permitting angular adjust- .1

ment with respect to the carrier 3. It should be noted at this time that the upper bolt 9' (see Fig ure 4) is longer than the bolt 9 and passes through a central opening in a top tie plate Ill that extends between the two guide posts 2 2. A coil spring ll encircles the bolt 9 and has its ends bearing against the tie plate l and a washer I2 is mounted on the bolt.

The rod resizing and feed roller housing C rotatably carries a shaft I3 on which is mounted a feed pinch roller M. The rollers l4 and M are designed to grip a heated cylindrical rod D therebetween and to move the rod longitudinally while rotating the rod. The rod is first heated to the proper temperature and is then introduced into a feed tube I5. The latter is carried by a feed tube support l6 (see Fig. 1) that is in turn supported by the guide posts 2-2.

The rod is then gripped by the rollers I l-M and is rotated and moved longitudinally into a central feed tube l1, also carried by the support IS. The speed of the longitudinal movement of the rod D is controlled by canting the rollers I4-l4'. It will be noted from Figures 1 and that the carriers 3 and 3 have two spaced lugs l8 andl8, respectively. Set screws l9 and I9 are adjustably carried by these lugs and bear against opposite sides of flanges 20 and 20 that are formed integral with the rod resizing and feed roller housings C and C. An adjustment of the set screws will swing the housings angularly and cant the rollers l4 and M at the desired angle. The set screws are locked against accidental movement after they have once been set.

Rod cutting and ball forming mechanism The rod cutting and ball forming mechanism is supported by frames E and E (see Figures 1 and 9). Both frames and their associated parts are identical and, therefore, a description of the frame E only will be given and the corresponding parts in the frame E will be primed. The frame E rests on the bed plate B and is adjustably seured thereto by bolts 21. The frame has a vertically extending guide 22 closed at its upper end by a header 23. The latter is secured to the frame by cap bolts 24, and the bolts in turn are removably secured to the frame by cap bolt keys 25.

A bottom carrier 26 (see Figure 9) is adjustably mounted within the guide 22 and also a feed tube cooling box 2'! and a top rider 28, are mounted above the carrier and within the guide. The bottom carrier 28 is supported by a pressure screw 29, which is threaded into a pressure nut 30 that rests in the frame E. A cast iron breaker 3|, or one of any other fragile material, is interposed between the bottom carrier 25 and the screw 29. This breaker will give way when the pressure on the carrier 26 exceeds a predeter-- mined point. The bottom carrier has a slotted flange at each side for receiving cap screws 32 for adjustably holding the carrier in place. A saddle groove 33 is formed in the top center of the carrier and receives a brass half bushing 3 The bushing may be made of any other antifriction material and is held in place by a projection 35 that enters a recess 36 in the bottom of the groove indicated at 33.

The feed cooling box 21 is also adjust-ably mounted in the guide 22 and has slotted flanges 31 (see Figures 6 and 7) for receiving cap screws 38, which adjustably hold the box in place. The box receives an end feeding tube 39, which is flanged for receiving the central feed tube IT.

A water jacket 40 surrounds the tube 39 and has a cold water inlet 4! and a hot water outlet 42. On each side of the tube, the water jacket is pierced by spring-receiving compartments 43. Springs 54 (see Figures 6, 7 and 9) are received in these compartments and have their outer ends bearing on the bottom carrier 25. A floating support for the box 21 is provided in this manner. A brass bushing 45 rests on the top of the box 21 and has a one-fourth circumferential groove therein for a purpose hereinafter described.

The top rider 28 also has slotted flanges 46 with cap screws 41 for adjustably securing it in the guide 22. The top rider is indentical to the bottom carrier and is turned upside down. A brass half bushing 48 is fitted into a groove 49 formed in the underside of the top rider. A pressure screw 50 extends through a pressure nut 5| and is spaced from the top rider by a cast iron breaker 52. The screws 29 and 50 are held against accidental rotation by pins 53 and 54 that extend through openings in the screw hand wheels 55 and 56.

The bottom carriers 26 and 26 rotatably support a, lower rod cutting and ball forming roller die 5! (see Figure 1). The brass quarter bushings 45 and 45' rotatably support an upper rod cutting and ball forming roller die 51. The roller die 5'! is connected by a. universal drive shaft 58 with the shaft l3 and in a like manner the roller die 51' is connected by a universal drive shaft 53 with the shaft I3.

The roller dies 5'! and 51 are identical and are provided with drunken or staggered helical threads 59 and 59, respectively. The initial portion of each thread is made narrow and sharp for the purpose of cutting into the heated rod. The space between the cutting edges of the threads at the lead end of the rollers is such as to receive the rod D. The cutting edges gradually enlarge in radii until the threads of the two roller dies abut each other after the threads have made one circumferential turn around the rollers. In other words, one complete revolution of both rollers willcause the cutting portions of the threads to sever completely a piece from the rod D. i l

' The width of the entrance of the helical groove in each roller die formed by the start of the cutting edge and a point 360 removed therefrom is about two-thirds of the diameter of the rod.

The helical groove on each roller die widens gradually until it has a width equal to that of the rod diameter and also of the ball which is simultaneously formed during the cutting operation. The sharp cutting edge of the initial portion of the thread also widens gradually so that the walls of the ball forming groove will have sufiicient width to withstand the necessary pressure needed to form the rod portion into a ball during the cutting operation. It is obvious that more than one thread may be provided on each roller.

In order to insure a complete severing of the rod D for each revolution of the rollers 51 and 51', I form a slight recess 60 in the thread 59 at a .point 360 from the start of the thread of the roller 51, and I form a slight cutting projection 60' in the thread 59' at a point 360 from the start of the thread on the roller 51' (see Figure 11). The two threads on the two rollers substantially contact each other at thi point and the projection 60 will, therefore, extend beyond the center of the rod D. This assures a complete severing of the rod by the cutting threads when the rollers have completed one revolution. The longitudinal movement of the rod D is such that the cutting threads merely cut into the rod and do not necessarily aid in advancing the rod.

The springs 44 permit a slight give to the end tube Stand will permit the tube to adjust itself automatically as the rod is fed therethrough and as the rod is subjected to cutting strains from both roller threads. It is sometimes advantageous to incline the cutting and forming roller axes slightly toward each other from the lead end to the rear end so that the shaping of the cut portion or segment of the rod into a ball will be progressively accomplished and will finally give a completed ball expelled from the rear ends of the rollers. The cutting of the rod and the simultaneous shaping of the piece into a ball during the cutting operation are completed in one revolution of the roller dies. The remaining thread portions define a grooved channel that smoothes the exterior ball surface.

The pressure screws 29' and 58' may, be ad justed for bringing the rear ends of the rollers are mounted on guide: rests 66 that are integral with theframes E'and. E. a

Bolts 61 arepassed through openings in the guide rests 56 and through slots 68 in the guide rest bars E i. Set screws 69 are received in the frames E and E and bear against lugs 10 that are integral with the guide rest bars. The set screws are independently adjustable for moving the guide plates into the proper position, after which the bolts 61 are tightened for rigidly securing the parts in place. The guide plates til cooperate with the rollers 51 and 5'5" in holding themetal balls between the rollers while they are being formed into spheres. The completed balls are fed into a ball outlet tube ltd (see Figure 1), after passing through the tube 39.

Mill operating mechanism The mechanism for operating the mill is illustrated in Figure 2. A gear box indicated generally at G has a drive shaft I! rotatably mounted therein and carrying a drive pinion 12. Any means desired may be utilized for ro tating the drive, shaft 1|. A driven shaft it is also rotatably mounted in the gear box and carries a pinion 14 that meshes with the pinion '12. A shaft 15 has a universal connection at one 7 end with the shaft 'I3and has a second universal 51 and 51' closer together than the front ends.

The shafts 58 and 53' with their universal joints at each end permit this movement.

I provide adjustable ball guides iii-ii! (see Figures 3 and 10), that extend along the sides of the rollers 51 and 51' to hold the metal balls F in the helical grooves while they are being formed. Each guide tl has a reduced edge. that extends between the rollers and the two edges are spaced apart a distance equal to the diameter of the ball. It will be noted from Fig ure 10 that the reduced edge 62 is formed with a Stellite surface and terminates in a blunt corner portion 63. This blunt corner is disposed at the leading ends of the rollers ti andii'i'. The ball guides iii are secured to guide rest bars 64 by bolts 65. Ihe guide rest bars 63 in turn connection at the other end with the roller die 51' (see Figures 1 and 2).

Novel means are provided forconnecting the roller die 51 with the shaft H and rmitting an angular adjustment to be effected between the two roller dies 51 and 51', if necessary. St is vita1 that the threads on the two die rollers p e g tly coincide so that the two roller grooves will rm a continuous ball forming passageway or guid way from end to end of the rollers. The inner end of the shaft H is keyed to a two-part housing 16 so that the housing will rotate with the shaft.

A stub shaft 11 is rotatably mounted in one wall of the gear box and has its other end rotatably disposed in the housing 16. A worm gear 18 is keyed to that portion of the stub shaft 11 that is rotatably received in the housing. The housing also carries a worm 19 that meshes with the worm gear 18 for a purpose presently to be described.

A pinion 89 is keyed to the stub shaft 11 and meshes with a pinion 8! that is mounted on a second driven shaft 82 similar to the driven shaft 13. A shaft 83, similar to the shaft l5, has a universal connection with the driven shaft 82 and has a second universal connection with the roller 51. In the event that the threads on the two roller dies 51 and 5'! should be out of registry,

the worm "i9 is rotated for turning the worm gear '58 in the housing #6. Thiswill rotate the stub shaft H with respect to the drive shaft 'H' and the two die rollers so that the projection 60' will be received in the recess fill for each complete rotation of the rollers. After the adjustment has been made, the worm 19 is locked against any accidental movement. Thereupon, the stub shaft ill, the worm I8 and the housing 16 will rotate as a unit with the drive'shaft H.

The worm [9 acts as a natural look for th worm gear, since the rotative movement is from the worm gear to the worm when the mill is operating. Of course, a worm gear of limited spiral angle cannot rotate a'worm. In addition to this, I mount and key the worm on a bolt 84, The ends of the bolt extend through the twopart housing 16, one end of the bolt being pro- Vided with a head and the other end with a nut (not shown). Both parts or halves of the twopart housing iii are identical in size and shape. The bolt 84 and the bolts 85 may be tightened after the angular adjustment has been made, thereby clamping the two-part housing together with sufficient force to grip the worm and prevent rotation of the latter. The two-part housing 16 and the worm 19 now will rotate as a unit and the pinions l2 and 8 will revolve at the same speed.

The mill can accommodate rods D of different diameters. In the event that the rods are smaller than the feed tubes, bushings (not shown) are placed in the tubes and different die rollers 57 and 51 ar mounted in place of the die rollers shown. A larger feed tube could be used when the rod is larger. A change in feed and forming rollers is necessary with each change in the diameter of the rod except where the pinch feed rollers reduce the diameter of the rod to the proper size as they feed the rod into the die rollers.

Operation From the foregoing description of the various parts of the mill, the operation thereof may be readily understood. The operation of the mill has been partially described when setting forth the several Pa Th rOd D is heated to a forging temperature to suit the material used. Any desired metal may b used for making the metal balls, such as rckel, chrome, or any high abrasive resisting alloys. The bar or rod, when heated to forging temperature, is inserted into the feed tube l5, where it is grasped by the pinch feed rollers l4 and It. These rollers have been previously canted to the desired degree for feeding the rod forwardly at the proper speed and also set at a correct opening in order to feed the correct amount of material for forming a proper size ball. Should the rod be slightly oversize, the pinch feed rollers would pinch or resize the rod to the proper diameter. The rod is fed through the feed tubes I1 and 39 and then reaches the rod cutting and ball forming roller dies 51 and 51. The pinch feed rollers advance the rod at the same speed as the threads 59 and 59 advance along the rollers while they rotate. There is, therefore, no longitudinal pulling action between the threads and the rod. Th rod is also rotated at the same peripheral speed as that of the rollers 5'! and 5'! by the pinch feed rollers and this prevents any peripheral slippage between the rod and roller dies 51 and 51. Small balls and balls of ductile material may be formed from unheated rods. The pinch feed rollers start moving the rod longitudinally and rotating the rod before the rod reaches the roller dies. There is no tearing action between the rod and dies due to lack of uniform movement therebetween.

The first revolution of the threads on each roller die will cause them to out through the rod.

In Figure 12 I show diagrammatically eight 1 stages of the circumferential cutting cycle. The projection 65 completes the severing of a rod portion from the remainder of the rod, and is illustrated in the last stage. The cutting of the rod and the shaping of the rod into a ball is done simultaneously in the first revolution of the dies while the rest of the helical grooves in the two rollers accomplish th'e'smoothing of the outer surface of the ball. The guides 6| hold the metal balls between the rollers during this process. The feed roller pressure screw nuts 4 and 4' are adjusted to exert the proper pressure on the rollers i4 and M to feed the rod longitudinally and also rotate it. The rollers M and I4 resize the rod if it is oversize. The feed rollers are driven at the same speed as the cutting and forming rollers and this prevents slippage between the rod D and the threads on the forming rollers.

The cutting portion of the threads on the form-- ing rollers increases in height from zero'to one half the diameter of the ball for one complete cycle of the thread. A cycle may be one fourth, one third, one half, a complete revolution or more, depending upon the number of threads on the roller and the size and hardness of the material. The cutting portion of the thread has a double cove contour with constant cove radii no matter what the thread height. This will cause the cut oil section to be nearly spherical when severed. The ball forming portion of the thread is made thicker to obtain suihcient strength to perform the side work of forming the cut portion of the rod into a sphere during the cutting action.

The eight stages of the circumferential travel cutting cycle is illustrated in Figure 12 and shows how the rod is simultaneously cut and shaped into a sphere. Stage I and stage I are the same stage. Figure compares the length of the cut rod portion with the diameter of the ball made from the same portion. If the ball diameter is one inch, then the length of the rod section will be 0.666 of one inch or of the ball diameter. Figure 14 shows diagrammatically 'howan oversized rod D is resized by the pinch feed rollers l4 and hi and further discloses what portions of the rod section are forced into places to form the completed ball. The rod section is shown at D and the completed ball is shown at F.

Referring to Figure 12, the development of the cutting thread is shown at 86 by the dot-dash line. The eight stages illustrate the step by step action of the cutting thread in cutting the rod and simultaneously forcing the material of each succeeding cylindrical portion of the rod into the form of a ball. This action is performed in the following progressive and orderly manner; stage 2 indicates the advancement of the rod D beyond the position of stage I and yet the rotation of the roller dies 51 and 57 causes the path 86 of the cutting edges 59 and 59 to form a negative lead of 0.110. The threads at this stage have cut into the rod diameter to reduce it from one inch to seven eighths of an inch. It will be noted that the concave portions of the groove adjacent to the cutting edge of the thread are shaped to form the lower part of the ball F into a spherical surface.

Stage 3 discloses the threads 59 and 59 as cutting still deeper into the rod D so that they are spaced three fourths of an inch from each other. The rod has advanced and the dies 5? and 5'! have rotated so that there is still a negative lead of the path of the cutting edge of 0.065. At stage t the negative lead of the cutting edge has been reduced to 0.008 and the threads 50 and 59' are five eighths of an inch apart. The concave portions adjacent to the threads are forming a spherical surface on the portion of the ball F attached to the rod and are forming a spherical surface on the rod end that will form the next ball F.

Stages 5 to 8 inclusive show the path 86 of the 9 cutting edge change from a negative to a positive lead of 0.0982 for stage a positive lead of 0.2008 for stage 6; a positive lead of 0.3128 for stage I; and a positive lead of 0.4336 for stage 8. During these four stages the threads 59 and 50 are progressively and uniformly advanced toward each other so that the distance between the threads is one-half an inch for stage 5; three-eighths of an inch for stage 6; one-fourth of an inch for stage 1; and one eighth of an inch for stage 8. The concave portions adjacent to the cutting threads continue to form the second half of the ball F and the first half of the next ball to be cut from the rod D. The concave ball-shaping portions create lines of force that are in a radial direction and toward the center of the ball.

The displacement of the material forming the ball results in the elongation of the axis of the cut portion of the cylinder into the diameter of the ball. To accomplish this result while the die rollers are rotating at a uniform speed and the rod material is being fed into the rollers at a uniform rate of two-thirds of the rod diameter per cycle of cutting operation, the cutting edges 59 and 59 must take the form shown in Figure 1. In stages 5 to 8 inclusive, the cutting threads widen as indicated in Figure 12. Stage I is the same as stage I and here the cutting projection 60 enters the recess 60, see Figure 11, for severing the ball F from the rod D. The remaining grooves on the dies smooth the ball surface.

During the rod cutting and ball forming cycle, the rod is advanced two-thirds of its own diameter as indicated by the line 81 in Figure 12. The cut rod portion is elongated one third of a diameter. Just before the ball is severed, the cutting threads are made thicker from stages 5 to 8 so that there is a space of one sixteenth of an inch between the ball F and the rod except for the actual point of attachment. The shearing projection 60' operates in this space to sever the ball.

The forming rollers and feed rollers may be tightened or loosened, as occasion demands, to form the proper ball. If the material runs over the die grooves, the feed rollers are-tightened slightly to resize the rod. On the other hand, if

the ball is not perfectly formed, the feed rollers are moved away from one another to permit a larger diameter rod to enter the dies. If the ball is too large, the formin rollers are brought closer together; if too small, they are separated. The

amount of stock to make a perfect ball of the.

correct size is governed by the pressure and the angle of cant of the feed rollers.

The device can be turned on its side if desired so that the die rollers will lie in a horizontal plane. The halls can be formed and dropped out from the dies without passing through the ball outlet tube 100,. The threads at the exit ends of the dies would stop short of the die ends and the bodies of the die rollers would be slightly reduced in diameter at their rear ends to permit the balls to dropout. Where the rollers are in a vertical plane, there can be side ejection of the balls before the balls reach the rear of the dies.

The drawings show the cutting cycle to occupy one revolution of the dies, but it is obvious that the cycle can be completed in a fraction of a revolution or one or more revolutions. Where multiple cutting threads are used, the cutting and ball forming cycles of the different threads may overlap each other. a

I claim:

1. In a ball formin mill, a pair of rod cutting and ball forming rollers having helical threads substantially abutting each other throughout the greater portions of their lengths and ball forming grooves disposed between the threads, the leading thread portions having cutting edges that gradually increase in height from points the same distance from the roller axes as the bottoms of the grooves to points where the two thread portions abut each other, concave walls disposed adjacent to the thread portions for forming the ball during the cutting operation, the remaining thread portions forming walls for smoothing the ball surface, and means for rotating the rollers, the opposed cutting portions of the roller threads where they abut each other being provided with a cooperating projection in one thread receivable in a recess in the other thread for causing the projection to extend beyond the midpoint between the two rollers.

A ball forming mill comprising a pair of rod feeding and rod rotating rollers, means for canting the rollers to the desired extent for controlling the longitudinal movement of the rod, a pair of rod cutting and ball forming the rollers operatively connected to the feed rollers and having spiral cutting and shaping threads, said second pair of rollers receiving the rod advanced by the first pair of rollers, means for adjusting the axes of the second pair of rollers toward or away from each other to the desired extent to cut the rod properly into pieces and for simultaneously forming the pieces into balls, and common means for simultaneously rotating the two pairszof rollers, said last named means in- 'gcluding means for rotating one roller of th second pair with respect to the other r0 r or the same pair for properly aligning the thread on the two ball forming rollers so that th grooves will provide a ball-forming channel. a. 3. A ball forming mill comprising a pair of rod feeding and rod rotating rollers, a pair of rod cutting and ball forming rollers axially aligned with the axes of said rod feeding rollers and. adapted to receive a rod advanced by the feeding rollers, said second-named rollers havin helical rod cutting and ball forming threads, means for rotating both sets of rollers at the same peripheral speed for causing the feed rollers to rotate and longitudinally advance the rod before it reaches the second pair of rollers so that the forward speed of the rod will be the same as the pitch of the threads and the rotational speed of the rod periphery will be the same as the rotational speed of the peripheries of the second pair of rollers; whereby the roller threads will sever the rod into portions and form the portions into ,balls, and means for canting the feed rollers at the desired angle for regulating the movement of the rod in the direction of itslength.

4. A ball forming mill comprising a pair of rod feeding and rod rotating rollers, means for canting the rollers to the desired extent for controlling the longitudinal movement of the rod, a pair of rod cutting and ball forming die rollers operatively connected to the feed rollers and having DAVID E. WELLS. 

